Terrestrial laser scanning (TLS) technology has various applications due to its capability of acquiring detailed 3D information about objects within a limited time-period. Yet, it is not widely used for the deformation monitoring of structures. To investigate the suitability of TLS for such tasks, a time-of-flight type Leica ScanStation C10 was used to determine the vertical deformations for two bridge load tests in Estonia, namely for the Loobu highway bridge and the Tartu railway overpass. The TLS results were verified with precise levelling, reflectorless tacheometry and dial gauges. Generally, deformation estimates obtained from TLS and other measurement techniques show sub-millimetre agreements (in terms of standard deviations). The maximum differences between the TLS and precise levelling results were 3.4 and 0.8 mm for the Loobu and the Tartu study, respectively. Since TLS has not yet reached the same accuracy as conventional geodetic high-precision techniques, it cannot fully replace them in high accuracy applications. However, TLS can be considered a complementary survey method for load tests as it provides valuable entire surface covering 3D information.

Regular as-built surveys have become a necessary input for building information modelling. Such large-scale 3D data capturing can be conducted effectively by combining structure-from-motion and unmanned aerial vehicles (UAV). Using a RTK-GNSS equipped UAV, 22 repeated weekly campaigns were conducted at two altitudes in various conditions. The photogrammetric approach yielded 3D models, which were compared to the terrestrial laser scanning based ground truth. Better than 2.8 cm geometry RMSE was consistently achieved using integrated georeferencing. It is concluded that the RTK-GNSS based georeferencing enables reaching better than 5 cm geometry accuracy by utilising at least one ground control point.

Computational stages of a new high-resolution 5 mm quasigeoid model for Estonia are explained. Certain requirements for the quality and coverage of gravity data in the context of 5 mm geoid modelling were fulfilled. The present gravity data coverage over the target area is 1 point per 10 km², less dense in adjacent land and marine areas. The average uncertainty estimate of gravity data within the target area is about 0.5 … 0.75 mGal. The gravity data were merged, cleaned, analysed, reduced and gridded to yield a seamless gravity anomaly field. A least squares modified Stokes formula (Sjöberg, L.E., 1991. Refined Least Squares Modification of Stokes Formula”. Manuscripta Geodaetica, 16, 367–375.) that combines local terrestrial gravity anomalies and the global geopotential model derived long-wavelength component in a truncated Stokes’s integral yielded the best gravimetric geoid modelling results. The combined uncertainty for most of the Estonian GNSS-levelling points is not exceeding 5 mm, allowing an adequate verification of the geoid modelling quality. Inter-comparison of the geoid model, GNSS-derived and spirit-levelled heights at discrete points was conducted for geoid modelling assessment. A two stage stochastic spatial prediction was applied to obtain an optimal fit between precise GNSS-levelling data and the geoid model. The location-specific post-fitting uncertainties of the resulting model EST-GEOID2017 revealed standard deviation of 4.2 mm, i.e. the same level as the accuracy of the used GNSS-levelling control points.